One of my personal projects I'm trying to update from 1.1 to 2.0 is my Quixo game program. My tests for the engine and framework all pass, but the ones for my "smart" engine (it uses an alpha-beta pruning algorithm rather than randomly picking a new move) are failing. I finally figured it out that it's due to my tests trying to load games that were stored using the binary formatter in 1.1. Seems like it can't read 'em in 2.0 (although the deserialization works in that Deserialize() doesn't crash, but the internal fields don't contain data). So...I'm going to update them using a more "resilient" serialization format (XML, hell, even JSON would be better).